Blasting apparatus and volumetric feeder

ABSTRACT

A blasting apparatus includes: a storage container including a storage chamber; a volumetric feeder; and a nozzle configured to project, together with compressed air, an abrasive supplied from the volumetric feeder, wherein: the volumetric feeder includes: a casing configured to define a space on an inside, and including an introduction port causing the space and the storage chamber to communicate with each other and a supply port opened toward a lower side in a position separated from the introduction port in a horizontal direction; and a screw including a rotational shaft housed in the casing and extending along the horizontal direction, the screw configured to carry the abrasive in the space toward the supply port from the introduction port by rotating about the rotational shaft; wherein the screw is housed in the casing in such a way as not to overlap the supply port in a vertical direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2021-018341filed with Japan Patent Office on Feb. 8, 2021, the entire contents ofwhich are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a blasting apparatus and a volumetricfeeder.

BACKGROUND

Blasting that performs surface treatment by projecting a solid-gastwo-phase flow consisting of an abrasive and gas toward an object to beprocessed by an injection nozzle has been widely known. Blasting is usedfor scale removal, flow line erasure, rust stripping, coating filmremoval, and surface preparation of a casting, for example. In recentyears, blasting is also used for applications in which a high treatmentaccuracy is required such as microfabrication and smooth finish of anelectronic component.

One requirement for realizing a high treatment accuracy is that theabrasive is stably supplied to the nozzle in a constant quantity. InJapanese Unexamined Patent Publication No. H07-328924, a blastingapparatus including a volumetric feeder that supplies a constantquantity of an abrasive to a nozzle is described. The blasting apparatushas a configuration in which a screw is provided in a lower portion of atank in which the abrasive is stored, and the abrasive discharged from ascrew pump is temporarily housed in a buffer and then is supplied to thenozzle via an abrasive supplying path.

Technical Problem

In the blasting apparatus disclosed in Japanese Unexamined PatentPublication No. H07-328924, by the buffer, fluctuation of the negativepressure generated in the nozzle for blasting and the fluctuation of thescrew are absorbed, and the performance of supplying of the abrasive tothe nozzle in a certain amount is improved. The negative pressure is asuction power of sucking the abrasive. However, in this blastingapparatus, the pressure loss of the path for supplying the abrasivebecomes high. Therefore, there is a need to increase the negativepressure. The negative pressure depends on the pressure of thecompressed air supplied to the nozzle. Therefore, compressed air ofwhich pressure is higher than that of the conventional art inevitablyneeds to be supplied. The pressure of the supplied compressed air isnormally set in accordance with a surface state that is the target ofthe blasting. When the pressure of the compressed air is set inaccordance with the suction power of the abrasive, the target surfacestate may not be obtained by the blasting. Conversely, when the pressureof the compressed air is set in accordance with the blasting forobtaining the target surface state, the supply amount of the abrasive tothe nozzle may become insufficient or the supply amount of the abrasivemay not be stable. In other words, in the blasting apparatus disclosedin Japanese Unexamined Patent Publication No. H07-328924, there is arisk that a constant quantity of the abrasive necessary to obtain thetarget surface state cannot be projected. Thus, the present disclosureprovides a technology capable of suppressing the increase and decreaseof the amount of an abrasive that is projected when a constant quantityof the abrasive is projected in a blasting apparatus.

Solution to Problem

A blasting apparatus according to one aspect of the present disclosureincludes a storage container, a volumetric feeder, and a nozzle forblasting. The storage container defines a storage chamber storing anabrasive in the storage chamber. The volumetric feeder supplies theabrasive to an outside of the storage container from the storagechamber. The nozzle projects, together with compressed air, the abrasivesupplied from the volumetric feeder. The volumetric feeder has a casingand a screw. The casing extends along a horizontal direction and definesa space on an inside. The casing has an introduction port causing thespace and the storage chamber to communicate with each other, and asupply port opened toward a lower side in a position separated from theintroduction port in the horizontal direction. The screw has arotational shaft housed in the casing and extending along the horizontaldirection. The screw carries the abrasive in the space toward the supplyport from the introduction port by rotating about the rotational shaft.The screw is housed in the casing in such a way as not to overlap thesupply port in a vertical direction.

In the blasting apparatus, the abrasive is introduced to the casing ofthe volumetric feeder from the storage chamber defined in the storagecontainer. In the volumetric feeder, the abrasive is carried toward thesupply port opened toward the lower side of the casing by the rotationof the screw. In the supply port, the supply port and the screw do notoverlap in the vertical direction, and hence the abrasive accumulated onthe screw does not fall down to the supply port. The abrasive that hasfallen down from the supply port is projected from the nozzle forblasting together with compressed air. The “nozzle for blasting” may behereinafter simply referred to as a “nozzle”. The supply port is openedtoward the lower side of the casing, and hence the distance from thesupply port to the nozzle can be reduced. As a result, the loss of theprojecting pressure due to the transfer of the abrasive can besuppressed. Therefore, when the blasting apparatus projects a constantquantity of abrasive, the blasting apparatus can suppress the increaseand decrease of the amount of the abrasive that is projected andsatisfactorily perform the blasting.

In one embodiment, the blasting apparatus may further include an airsupplying member. The air supplying member may be housed in the storagechamber, connected to an air source, and have a plurality of air holessupplying air from the air source provided therein. In this case, air issupplied to the abrasive stored in the storage container and theabrasive is fluidized. The blasting apparatus can suppress bridging inwhich the abrasive adheres to the inner wall of the storage container.Bridging is also referred to as scaffolding.

In one embodiment, the blasting apparatus may further include aconnection pipe. The connection pipe may connect the nozzle and thesupply port of the casing to each other. The nozzle may be provided insuch a way as to cause a relative positional relationship with thecasing to be fixed. In this case, the attitude of the nozzle is limitedto the position of the casing, and hence the connection pipe is notdeformed in accordance with the nozzle. Therefore, the blastingapparatus can avoid a case where the flow of the abrasive changes inaccordance with the deformation of the connection pipe. Therefore, theblasting apparatus can suppress the increase and decrease of the amountof the abrasive that is projected.

In one embodiment, the nozzle may include a nozzle body, an air nozzle,and an injection nozzle. The nozzle body may be coupled to a paththrough which the abrasive is transferred toward the nozzle from thevolumetric feeder. The air nozzle may introduce the compressed air intothe nozzle body and generate an air flow sucking the abrasive into thenozzle body. The injection nozzle may project, together with thecompressed air, the abrasive transferred into the nozzle body. Thenozzle may be disposed in such a way as to cause a pressure lossgenerated in accordance with the generation of the air flow to be 0.1kPa or less.

In one embodiment, the blasting apparatus may further include arestriction plate. In the restriction plate, an opening passing throughthe restriction plate in a thickness direction may be formed. Therestriction plate may be disposed between a distal end of the screw andthe supply port in such a way as to partition an inside of the casing.In this case, the abrasive that has been carried by the screw is pressedagainst the restriction plate. As a result, the abrasive that has passedthrough the opening of the restriction plate is compressed to apredetermined bulk density. Therefore, the blasting apparatus can causethe bulk density of the abrasive that is sent out to the nozzle to bestable.

In one embodiment, the blasting apparatus may further include arestriction plate. The restriction plate may be fixed to a distal end ofthe screw in such a way as to form a gap between the restriction plateand an inner wall of the casing. In this case, the abrasive that hasbeen carried by the screw is pressed against the restriction plate. As aresult, the abrasive that has passed through the gap formed between therestriction plate and the inner wall of the casing is compressed to apredetermined bulk density. Therefore, the blasting apparatus can causethe bulk density of the abrasive that is sent out to the nozzle to bestable.

In one embodiment, the blasting apparatus may further include a movementmechanism. The storage container, the volumetric feeder, and the nozzlemay configure a unit, and the movement mechanism may relatively move theunit with respect to an object to be processed. The blasting apparatuscan perform blasting on the object to be processed in a state in whichthe nozzle and the volumetric feeder are unitized.

A volumetric feeder according to another aspect includes a casing and ascrew. The casing extends along a horizontal direction and defines aspace on an inside. The casing has an introduction port for introducingthe abrasive to the space, and a supply port opened toward a lower sidein a position separated from the introduction port in the horizontaldirection. The screw has a rotational shaft housed in the casing andextending along the horizontal direction. The screw carries the abrasivein the space toward the supply port from the introduction port byrotating about the rotational shaft. The screw is housed in the casingin such a way as not to overlap the supply port in a vertical direction.

In the volumetric feeder, the abrasive is carried toward the supply portopened toward the lower side of the casing by the rotation of the screw.In the supply port, the supply port and the screw do not overlap in thevertical direction, and hence the abrasive accumulated on the screw doesnot fall down to the supply port. The abrasive that has fallen down fromthe supply port is projected from the nozzle for blasting together withcompressed air. Therefore, the volumetric feeder can suppress theincrease and decrease of the amount of the abrasive when a constantquantity of abrasive is supplied to the blasting apparatus.

Advantageous Effect of Invention

According to the technology according to the present disclosure, theincrease and decrease of the amount of the abrasive that is projectedcan be suppressed and the blasting can be satisfactorily performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view illustrating one example of a blastingapparatus including a volumetric feeder according to an embodiment;

FIG. 2 is a schematic view illustrating a part of a blasting apparatusaccording to a modified example;

FIG. 3 is a schematic view illustrating a part of a blasting apparatusaccording to another modified example;

FIG. 4 is a schematic view illustrating a modified example of arestriction plate;

FIG. 5 is a schematic view illustrating another modified example of arestriction plate;

FIG. 6 is a schematic view illustrating another modified example of arestriction plate; and

FIG. 7 is an entire view illustrating a blasting apparatus according toan example.

DETAILED DESCRIPTION

An embodiment of the present disclosure will be described below withreference to the drawings. In the description below, the same orequivalent elements are denoted by the same reference characters, andoverlapping description is not repeated. Dimension ratios of thedrawings do not necessarily match with those described. Terms “up”,“down”, “left”, and “right” are based on the illustrated states and arefor convenience.

[Configuration of Blasting Apparatus]

FIG. 1 is an entire view illustrating one example of a blastingapparatus including a volumetric feeder according to the embodiment. Ablasting apparatus 1 illustrated in FIG. 1 is an apparatus that projectsan abrasive M and is configured as a so-called suction-type blastingapparatus. The suction-type blasting apparatus is a gravity-typeblasting apparatus in other words. As illustrated in FIG. 1, theblasting apparatus 1 includes a storage container 10, a volumetricfeeder 20, and a nozzle 30. The storage container 10 defines a storagechamber S in which the abrasive M is stored on the inside and stores theabrasive M therein. The storage container 10 is connected to thevolumetric feeder 20.

The volumetric feeder 20 is an apparatus that sends out the abrasive Mstored in the storage container 10 to the outside. The volumetric feeder20 is a screw feeder, for example, and continuously sends out theabrasive M stored in the storage container 10 by a constant quantity.The volumetric feeder 20 is disposed on the lower side of the storagecontainer 10. A part of the volumetric feeder 20 may be housed in alower portion of the storage container 10. The volumetric feeder 20includes a casing 21 and a screw 24 housed in the casing 21.

The casing 21 is a hollow-cylinder-shaped member extending along thehorizontal direction. In the casing 21, a space V is defined. The casing21 has an introduction port 22 that causes the storage chamber S of thestorage container 10 and the space V to communicate with each other. Theintroduction port 22 is opened toward the upper side, for example. Theabrasive M is introduced into the space V of the volumetric feeder 20from the storage chamber S of the storage container 10 via theintroduction port 22. The casing 21 has a supply port 23 in a positionseparated from the introduction port 22 in the horizontal direction. Thesupply port 23 is opened toward the lower side of the casing 21. Thesupply port 23 is formed in a lower portion of the casing 21 in such away as to cause the abrasive M carried by the screw 24 to fall down. Thesupply port 23 causes the abrasive M to fall down and sends the abrasiveM to the nozzle 30.

The screw 24 is housed in the space V in the casing 21. The screw 24 hasa rotational shaft 24 a and blades 24 b. The rotational shaft 24 a ishoused in the casing 21 and extends along the horizontal direction. Theblades 24 b are helicoidally fixed to an outer peripheral surface of therotational shaft 24 a in such a way as to cause two blades 24 b adjacentto each other to be arranged at a predetermined interval. The screw 24is rotatably supported by a first bearing portion 26 a and a secondbearing portion 26 b. The first bearing portion 26 a and the secondbearing portion 26 b are members including a bearing and a supportportion of the bearing. The screw 24 is coupled to a motor 25 and isrotationally driven about the rotational shaft 24 a. The abrasive M thathas come between the adjacent two blades 24 b is carried to the supplyport 23 of the casing 21 by the rotational driving of the screw 24.

The screw 24 is housed in the casing 21 in such a way as not to overlapthe supply port 23 in the vertical direction. For example, when thescrew 24 is rotatably supported by the first bearing portion 26 a andthe second bearing portion 26 b in a cantilever manner near theintroduction port 22, the screw 24 extends toward the supply port 23from the introduction port 22 to a position that does not overlap thesupply port 23 in the vertical direction. In other words, the screw 24does not exist above the supply port 23.

The supply port 23 of the casing is connected to the nozzle 30 via aconnection pipe 31. The connection pipe 31 transfers the abrasive M sentout from the supply port 23 to the nozzle 30. The connection pipe 31defines a flow path capable of transferring the abrasive M on theinside. The connection pipe 31 is a hose made of resin, or a pipe madeof metal, for example.

The nozzle 30 projects, together with compressed air, the abrasive Msupplied from the connection pipe 31. The nozzle 30 includes a nozzlebody 30 a, an air nozzle 30 b inserted from one end side of the nozzlebody, and an injection nozzle 30 c inserted into the other end side ofthe nozzle body. The compressed air is supplied into the nozzle body 30a from an air pipe 32 connected to the air nozzle 30 b. By an ejectorphenomenon by the compressed air projected from the air nozzle 30 b, anegative pressure is generated in the nozzle body 30 a. The negativepressure generated in the nozzle body 30 a generates an air flow in theconnection pipe 31 connected to the nozzle body 30 a. The abrasive M istransferred to the nozzle body 30 a from the supply port 23 by the airflow generated in the connection pipe 31. The transferred abrasive M ismixed with the compressed air in the nozzle body 30 a. By the injectionnozzle 30 c, the abrasive M is projected onto a workpiece W as asolid-gas two-phase flow with the compressed air.

The workpiece W is an object to be processed that is the target ofblasting. As one example, the workpiece W is a hard brittle materialsuch as glass, silicon, and ceramics, various metals, or compositematerials such as a carbon fiber reinforced plastics (CFRP) material andglass fiber reinforced plastics (GFRP). The workpiece W is placed on atable 33.

The table 33 is a board on which the placed workpiece W is fixed duringthe blasting. For example, the table 33 has a placing surface thatadsorbs the workpiece W. The table 33 is disposed in such a way as tointersect with the projecting direction of the nozzle 30. The table 33may move the position of the workpiece W relative to the nozzle 30.

A treatment container 3 defines a processing chamber P on the inside andhouses the nozzle 30, the workpiece W, and the table 33. The blasting isperformed in the processing chamber P. The abrasive M projected onto theworkpiece W as a solid-gas two-phase flow of compressed air falls downto a lower portion of the processing chamber P with swarf of theworkpiece W. The abrasive M and the swarf of the workpiece W that havefallen down to the lower portion of the processing chamber P arecollected by a collection pipe 12. The collection pipe 12 connects theprocessing chamber P of the treatment container 3 and a classificationmechanism 11 to each other.

The classification mechanism 11 collects the abrasive M and the swarf ofthe workpiece W that have fallen down to the lower portion of theprocessing chamber P through the collection pipe 12. The classificationmechanism 11 separates the abrasive M and the swarf of the workpiece Wthat have been collected. The classification mechanism 11 is acyclone-type classification machine, for example. The classificationmechanism 11 separates the abrasive M that can be reused, and theabrasive M and the swarf of the workpiece W that cannot be reused. Theabrasive M that can be reused is returned to the storage container 10.The abrasive M and the swarf of the workpiece W that cannot be reusedare collected in a dust collector 2.

The dust collector 2 is an apparatus that collects the abrasive M andthe swarf of the workpiece W that cannot be reused. The dust collector 2is connected to the classification mechanism 11. The dust collector 2generates a negative pressure. The negative pressure of the dustcollector 2 generates an air flow in the classification mechanism 11 andthe collection pipe 12 connected to the classification mechanism 11. Theabrasive M and the swarf of the workpiece W that cannot be reused travelon the air flow and are sucked into the dust collector 2. The abrasive Mand the swarf of the workpiece W having been sucked that cannot bereused are collected in the dust collector 2 by a filter, for example.

The blasting apparatus 1 is controlled by a control device 4. Thecontrol device 4 is configured as a programmable logic controller (PLC),for example. The control device 4 may be configured as a computer systemincluding a processor such as a central processing unit (CPU), a memorysuch as a random access memory (RAM) and a read only memory (ROM), aninput-output device such as a touch screen, a mouse, a keyboard, and adisplay, and a communication device such as a network card. The controldevice 4 realizes a function of the control device 4 by causing eachhardware to operate under the control of the processor based on acomputer program stored in the memory. For example, the control device 4controls the pressure of the compressed air supplied from the air pipe32. The control device 4 controls the amount of the abrasive M that thevolumetric feeder 20 sends out. The control device 4 may control atleast any one of the projecting amount of the abrasive, the pressure bywhich the abrasive M is projected, and the positional relationshipbetween the nozzle 30 and the workpiece W.

As above, according to the blasting apparatus 1 and the volumetricfeeder 20 according to the embodiment, the abrasive M is introduced tothe casing 21 of the volumetric feeder 20 from the storage chamber Sdefined in the storage container 10. In the volumetric feeder 20, theabrasive M is carried toward the supply port 23 opened toward the lowerside of the casing 21 by the rotation of the screw 24. In the supplyport 23, the supply port 23 and the screw 24 do not overlap in thevertical direction, and hence the abrasive M accumulated on the screw 24does not fall down to the supply port 23. The abrasive M that has fallendown from the supply port 23 is projected from the nozzle 30 forblasting together with compressed air. Therefore, the blasting apparatus1 and the volumetric feeder 20 can suppress the increase and decrease ofthe amount of the abrasive that is projected.

The blasting apparatus 1 of the present disclosure may be variouslyomitted, replaced, and changed.

[Modified Example of Connection Between Volumetric Feeder and Nozzle]

FIG. 2 is a schematic view illustrating a part of a blasting apparatusaccording to a modified example. In the blasting apparatus illustratedin FIG. 2, the nozzle 30 may be connected to the supply port 23 of thecasing 21 in such a way as to cause the relative positional relationshipwith the casing 21 to be fixed. For example, the nozzle 30 is connectedto the supply port 23 by the connection pipe 31 made of metal. As aresult, the relative positional relationship between the nozzle 30 andthe casing 21 is fixed. Alternatively, the relative portion between thenozzle 30 and the casing 21 may be fixed as a result of the nozzle 30and the volumetric feeder 20 being fixed to a frame member that is notillustrated. When the nozzle 30 and the volumetric feeder 20 are fixedto the frame member, the connection pipe 31 may be a hose made of resin.

A pressure loss is generated in a path through which the abrasive M istransferred to the nozzle 30 from the supply port 23 of the casing 21.The pressure loss is a friction loss generated between the connectionpipe 31 forming the flow path and the air flow flowing through the flowpath. The flow amount of the abrasive M transferred in the connectionpipe 31 by the air flow changes in accordance with the pressure loss.The pressure loss changes in accordance with the entire length and theshape of the flow path. When the entire length of the flow path extendsor when the flow path is curved, the pressure loss increases. Forexample, when the relative positional relationship between the nozzle 30and the casing 21 changes, the entire length and the shape of the flowpath changes in accordance with the relative positional relationshipbetween the nozzle 30 and the casing 21. In this case, by the increaseand decrease of the pressure loss, the flow amount of the abrasive Mtransferred to the nozzle 30 fluctuates. As a result of the relativepositional relationship between the nozzle 30 and the casing 21 beingfixed, a case where the flow path through which the abrasive M istransferred between the supply port 23 of the casing 21 and the nozzle30 is deformed is avoided, and the flow amount of the abrasive Mtransferred to the nozzle 30 becomes stable.

If the pressure loss of the path is large when the abrasive to beprojected from the injection nozzle is drawn from the volumetric feeder,there are cases where the abrasive cannot be sufficiently sucked. Whenthe nozzle 30 is disposed in a position in which the pressure lossbecomes large, the pressure of the compressed air introduced to thenozzle 30 may be further increased in order to obtain a negativepressure, that is, a suction power with which the abrasive M can besufficiently sucked. However, the pressure by which the abrasive M isprojected also increases, and hence the performance of the blasting alsoinevitably improves. As a result, the blasting may become an excessivetreatment for the surface state that is the target. Therefore, thenozzle 30 needs to be disposed in such a way as to cause a negativepressure with which the abrasive M is sufficiently sucked to beobtained. In order to do so, the position in which the nozzle 30 isdisposed may be adjusted in such a way as to cause the pressure loss tobe 0.1 kPa or less.

In the blasting apparatus illustrated in FIG. 2, the storage container10, the volumetric feeder 20, and the nozzle 30 are integrallyconfigured and may configure a unit 5. For example, the unit 5 is a partof the blasting apparatus 1 obtained by integrally configuring thestorage container 10, the volumetric feeder 20, and the nozzle 30 as amovable unit. In the unit 5, the nozzle 30 may be connected to thesupply port 23 of the casing 21 via the connection pipe 31 in such a wayas to cause the relative positional relationship with the casing 21 tobe fixed. The unit 5 and the workpiece W are housed in the processingchamber P defined in the treatment container 3 illustrated in FIG. 1.

The blasting apparatus illustrated in FIG. 2 may include a movementmechanism 60 that causes the unit 5 to move relative to the workpiece W.The movement mechanism 60 moves the unit 5 with respect to the workpieceW. The movement mechanism 60 can be a three-axis orthogonal robot thatchanges the vertical position (X-direction), the horizontal position(Y-direction), and the height position (Z-direction) of the unit 5, forexample. The position of the nozzle 30 that projects the abrasive Mchanges in accordance with the position to which the movement mechanism60 moves the unit 5. The movement mechanism 60 changes the position ofthe unit 5 on the basis of the blasting condition and the size of theworkpiece W.

As above, in the blasting apparatus illustrated in FIG. 2, the relativepositional relationship between the nozzle 30 and the casing 21 may befixed. In this case, the entire length and the shape of the flow paththrough which the abrasive M is transferred does not change includingduring the blasting. The attitude of the nozzle 30 is limited to theposition of the casing 21, and hence the connection pipe 31 is notdeformed in accordance with the nozzle. Therefore, the blastingapparatus can avoid a case where the flow of the abrasive M changes inaccordance with the deformation of the connection pipe 31 and hence canperform stable blasting. In the blasting apparatus illustrated in FIG.2, the table 33 that moves the position of the workpiece W relative tothe nozzle 30 does not necessarily need to be housed in the treatmentcontainer 3, and hence downsizing can be performed as compared to theblasting apparatus that moves the workpiece W relative to the nozzle 30.

[Modified Example of Storage Container and Volumetric Feeder]

FIG. 3 is a schematic view illustrating a part of a blasting apparatusaccording to another modified example. The blasting apparatusillustrated in FIG. 3 includes an air supplying member 40 housed in thestorage container 10.

The air supplying member 40 is a member that causes the abrasive Mstored in the storage container 10 to easily flow to the introductionport 22. The air supplying member 40 is connected to an air source 41and a plurality of air holes that supply air from the air source 41 isprovided. As one example, the air supplying member 40 is sintered metaland is a porous member. The air source 41 is an air blowing machine, acompressing machine, or a blower, for example.

The fluidity of the abrasive M stored in the storage container 10 mayincrease by air supply from the air supplying member 40. The fluidity ofpowder is the ease of flow of powder. Powder of which fluidity is highexhibits a behavior close to a liquid phase. Powder of which fluidity islow exhibits a behavior close to a solid phase. The fluidity of powderis determined on the basis of the amount of air that the powderincludes, the particle diameter configuring the powder, the physicalproperty of the particle, and the like. In the storage container 10, airmay be supplied to the abrasive M from the air holes of the airsupplying member 40, and the fluidity of the stored abrasive M mayimprove. The blasting apparatus can suppress the adhesion of theabrasive M to the inside of the storage container 10.

The blasting apparatus illustrated in FIG. 3 may include a restrictionplate 50 disposed between a distal end of the screw 24 and the supplyport 23 in such a way as to partition the inside of the casing 21. Therestriction plate 50 is a member for causing the bulk density of theabrasive M in the casing 21 to be fixed. The restriction plate 50 is adisk member, for example. As one example, the restriction plate 50 isfixed to a distal end of the screw 24. In the restriction plate 50, anopening passing therethrough in the thickness direction is formed. Thethickness direction of the restriction plate 50 matches with thehorizontal direction of the casing 21. The opening is provided in such away as to enable the abrasive M carried by the screw 24 to passtherethrough. The opening may be formed in the restriction plate 50 in aplurality of numbers at a predetermined interval.

A constant quantity of the abrasive M out of the abrasive M stored inthe storage container 10 is introduced into the casing 21 from theintroduction port 22. The abrasive M is carried toward the supply port23 by the rotation of the screw 24. When the abrasive M reaches therestriction plate 50, the abrasive M that has been carried by the screw24 is pressed against the restriction plate 50. As a result, theabrasive M that has passed through the opening of the restriction plate50 is compressed to a predetermined bulk density. Therefore, theblasting apparatus 1 can cause the bulk density of the abrasive M thatis sent out to the nozzle 30 to be stable.

[Another Modified Example of Restriction Plate]

The blasting apparatus 1 may include the restriction plate 50 fixed tothe distal end of the screw 24 in such a way as to form a gap betweenthe restriction plate 50 and an inner wall of the casing 21. In thiscase, an opening does not necessarily need to be formed in therestriction plate 50. The abrasive M that has been carried by the screw24 is pressed against the restriction plate 50. As a result, theabrasive M that has passed through the gap formed between therestriction plate 50 and the inner wall of the casing 21 is compressedto a predetermined bulk density. Therefore, the blasting apparatus 1 cancause the bulk density of the abrasive that is sent out to the nozzle 30to be stable.

FIG. 4 is a schematic view illustrating a modified example of arestriction plate. As illustrated in FIG. 4, the restriction plate 50may be fixed on the inner side of the casing 21 at a position betweenthe distal end of the screw 24 and the supply port 23. In other words,the restriction plate 50 does not necessarily need to rotate togetherwith the screw 24.

FIG. 5 is a schematic view illustrating another modified example of therestriction plate 50. As illustrated in FIG. 5, the restriction plate 50may be integrally provided with the second bearing portion 26 b on theinner side of the casing 21 at a position between the distal end of thescrew 24 and the supply port 23. In this case, an opening is provided ina bearing support portion of the second bearing portion 26 b. The screw24 is rotatably supported by the first bearing portion 26 a near theintroduction port 22 and the second bearing portion 26 b (restrictionplate 50) near the supply port 23 in a double-supported manner.

FIG. 6 is a schematic view illustrating another modified example of therestriction plate 50. The blasting apparatus 1 according to FIG. 6 mayinclude the restriction plate 50 fixed to the distal end of the screw24, and the restriction plate 50 (second bearing portion 26 b)integrally provided with the second bearing portion 26 b on the innerside of the casing 21 at a position between the distal end of the screw24 and the supply port 23. The screw 24 is rotatably supported by thefirst bearing portion 26 a near the introduction port 22 and the secondbearing portion 26 b (restriction plate 50) near the supply port 23 in adouble-supported manner. The rotational shaft 24 a of the screw 24extends beyond the second bearing portion 26 b (restriction plate 50).The restriction plate 50 fixed to the distal end of the screw 24 isdisposed closer to the supply port 23 than the second bearing portion 26b (restriction plate 50).

Other Modified Examples

The nozzle 30 does not necessarily need to be connected to the supplyport 23 in such a way as to cause the relative positional relationshipwith the introduction port 22 of the casing 21 to be fixed. The storagecontainer 10, the volumetric feeder 20, and the nozzle 30 do notnecessarily need to configure the unit 5. The blasting apparatus 1 doesnot necessarily need to include the movement mechanism 60 that causesthe unit 5 to move relative to the workpiece W.

The blasting apparatus 1 does not necessarily need to include the airsupplying member 40 which is housed in the storage container 10 andconnected to the air source 41 and in which the plurality of air holesthat supply air from the air source 41 is provided. The blastingapparatus 1 does not necessarily need to include the restriction plate50 in which the opening passing therethrough in the thickness directionis formed and which is disposed between the distal end of the screw 24and the supply port 23 in such a way as to partition the inside of thecasing 21. The blasting apparatus 1 does not necessarily need to includethe restriction plate 50 fixed to the distal end of the screw 24 in sucha way as to form a gap between the restriction plate 50 and the insideof the casing 21.

The blasting apparatus 1 may be a direct-pressure-type blastingapparatus. The blasting apparatus 1 may be a wet-type blastingapparatus. When the abrasive M is not reused, the blasting apparatus 1does not necessarily need to include the classification mechanism 11 andthe dust collector 2. In this case, an operator may supply the abrasiveM to the storage container 10.

The movement mechanism 60 is not limited to an orthogonal robot. Themovement mechanism 60 may be an articulated robot, a parallel linkrobot, and a SCARA robot, for example.

[Verification of Arrangement and Blast Condition of Nozzle]

The arrangement and the blast condition of the nozzle 30 with which thepressure loss in the path when the abrasive is induced from thevolumetric feeder becomes 0.1 kPa or less was examined.

Example

A blasting apparatus 1A illustrated in FIG. 7 was used. In the blastingapparatus 1A, the nozzle 30 was disposed below the volumetric feeder 20.The nozzle 30 was the same as the nozzle 30 of the blasting apparatus 1.The diameter of the caliber of the injection nozzle 30 c was φ8 mm. Thenozzle body 30 a and the volumetric feeder 20 were connected to eachother with use of the connection pipe 31. Other configurations were thesame as the blasting apparatus 1 illustrated in FIG. 1. As the blastcondition, the projecting pressure was set to 150 kPa to 600 kPa, andgreen carborundum GC #600 manufactured by SINTOKOGIO, LTD. was used asthe abrasive M. Pressure sensors were provided on the upstream side andthe downstream side of the connection pipe 31, and the difference in thedetection results of the pressure sensors obtained during the blastingwas set to be the pressure loss of the connection pipe 31. Theprojecting amount from the nozzle 30 was measured. The results areillustrated in Table 1.

Comparative Example

In the blasting apparatus 1A illustrated in FIG. 7, the arrangementposition of the volumetric feeder and the length of a supplying pathfrom the volumetric feeder to the nozzle were changed. The volumetricfeeder was disposed in such a way as to be positioned below the nozzle30. Instead of the connection pipe 31, a hose having a length that isten times or more of the connection pipe 31 was used. As the blastcondition, the projecting pressure was set to 50 kPa to 600 kPa. Otherblast conditions were the same as those of the example. The differencein the detection results of the pressure sensors obtained during theblasting was set to be the pressure loss of the hose. The projectingamount from the nozzle 30 was measured. The results are illustrated inTable 1.

TABLE 1 Example Comparative example Projecting pressure 50-600 150-600[kPa] Projecting amount Up to 500 (when Up to 150 (when [g/min]projecting pressure is projecting pressure is 50 kPa) 150 kPa) Pressureloss [kPa] 0.1 or less More than 0.1

Table 1 is a table showing the measurement results of the pressure loss.As shown in Table 1, it was confirmed that the pressure loss became 0.1kPa or less when the projecting pressure was in the range of 50 kPa to600 kPa in the example. When the projecting pressure was 50 kPa, theprojecting amount of the abrasive M became 500 g/min and the pressureloss became 0.1 kPa or less. In other words, it was confirmed that theabrasive M was stably projected even at an extremely low pressurebecause the pressure loss was small in the example. It was confirmedthat the pressure loss was more than 0.1 kPa when the projectingpressure was in the range of 150 kPa to 600 kPa in the comparativeexample. When the projecting pressure was 150 kPa, the projecting amountof the abrasive M became 150 g/min and the pressure loss became morethan 0.1 kPa. This indicates that the projecting of the abrasive Mcaused pulsation at an extremely low pressure and the lowest usablepressure became high because the pressure loss was large in thecomparative example. Therefore, it was confirmed that the abrasive M wasnot stably projected under a low-pressure condition and only a smallamount was stably projected even at the lowest usable pressure in thecomparative example.

REFERENCE SIGNS LIST

1 . . . Blasting apparatus, 10 . . . Storage container, 20 . . .Volumetric feeder, 21 . . . Casing, 22 . . . Introduction port, 23 . . .Supply port, 24 . . . Screw, 24 a . . . Rotational shaft, 30 . . .Nozzle, 30 a . . . Nozzle body, 30 b . . . Air nozzle, 30 c . . .Injection nozzle, 31 . . . Connection pipe, 40 . . . Air supplyingmember, 41 . . . Air source, 50 . . . Restriction plate, 60 . . .Movement mechanism, M . . . Abrasive, S . . . Storage chamber, V . . .Space.

What is claimed is:
 1. A blasting apparatus configured to project anabrasive, the blasting apparatus comprising: a storage containerconfigured to define a storage chamber storing the abrasive in thestorage chamber; a volumetric feeder configured to supply the abrasiveto an outside of the storage container from the storage chamber; and anozzle configured to project, together with compressed air, the abrasivesupplied from the volumetric feeder, wherein: the volumetric feederincludes: a casing extending along a horizontal direction, configured todefine a space on an inside, and including an introduction port and asupply port, the introduction port configured to cause the space and thestorage chamber to communicate with each other, and the supply portopened toward a lower side in a position separated from the introductionport in the horizontal direction; and a screw including a rotationalshaft housed in the casing and extending along the horizontal direction,the screw configured to carry the abrasive in the space toward thesupply port from the introduction port by rotating about the rotationalshaft; wherein the screw is housed in the casing in such a way as not tooverlap the supply port in a vertical direction.
 2. The blastingapparatus according to claim 1, further comprising an air supplyingmember housed in the storage chamber, connected to an air source, andincluding a plurality of air holes configured to supply air from the airsource provided therein.
 3. The blasting apparatus according to claim 1,further comprising a connection pipe connecting the nozzle and thesupply port of the casing to each other, wherein the nozzle is providedin such a way as to cause a relative positional relationship with thecasing to be fixed.
 4. The blasting apparatus according to claim 2,further comprising a connection pipe connecting the nozzle and thesupply port of the casing to each other, wherein the nozzle is providedin such a way as to cause a relative positional relationship with thecasing to be fixed.
 5. The blasting apparatus according to claim 1,wherein: the nozzle includes: a body coupled to a path through which theabrasive is transferred toward the nozzle from the volumetric feeder; anair nozzle configured to introduce the compressed air into the body andconfigured to generate an air flow sucking the abrasive into the body;and an injection nozzle configured to project, together with thecompressed air, the abrasive transferred into the body; and the nozzleis disposed in such a way as to cause a pressure loss generated inaccordance with the generation of the air flow to be 0.1 kPa or less. 6.The blasting apparatus according to claim 2, wherein: the nozzleincludes: a body coupled to a path through which the abrasive istransferred toward the nozzle from the volumetric feeder; an air nozzleintroducing the compressed air into the body and configured to generatean air flow sucking the abrasive into the body; and an injection nozzleprojecting, together with the compressed air, the abrasive transferredinto the body; and the nozzle is disposed in such a way as to cause apressure loss generated in accordance with the generation of the airflow to be 0.1 kPa or less.
 7. The blasting apparatus according to claim3, wherein: the nozzle includes: a body coupled to a path through whichthe abrasive is transferred toward the nozzle from the volumetricfeeder; an air nozzle introducing the compressed air into the body andconfigured to generate an air flow sucking the abrasive into the body;and an injection nozzle projecting, together with the compressed air,the abrasive transferred into the body; and the nozzle is disposed insuch a way as to cause a pressure loss generated in accordance with thegeneration of the air flow to be 0.1 kPa or less.
 8. The blastingapparatus according to claim 1, comprising a restriction plate in whichan opening passing through the restriction plate in a thicknessdirection is formed, the restriction plate being disposed between adistal end of the screw and the supply port in such a way as topartition an inside of the casing.
 9. The blasting apparatus accordingto claim 2, comprising a restriction plate in which an opening passingthrough the restriction plate in a thickness direction is formed, therestriction plate being disposed between a distal end of the screw andthe supply port in such a way as to partition an inside of the casing.10. The blasting apparatus according to claim 3, comprising arestriction plate in which an opening passing through the restrictionplate in a thickness direction is formed, the restriction plate beingdisposed between a distal end of the screw and the supply port in such away as to partition an inside of the casing.
 11. The blasting apparatusaccording to claim 4, comprising a restriction plate in which an openingpassing through the restriction plate in a thickness direction isformed, the restriction plate being disposed between a distal end of thescrew and the supply port in such a way as to partition an inside of thecasing.
 12. The blasting apparatus according to claim 1, comprising arestriction plate fixed to a distal end of the screw in such a way as toform a gap between the restriction plate and an inner wall of thecasing.
 13. The blasting apparatus according to claim 2, comprising arestriction plate fixed to a distal end of the screw in such a way as toform a gap between the restriction plate and an inner wall of thecasing.
 14. The blasting apparatus according to claim 3, comprising arestriction plate fixed to a distal end of the screw in such a way as toform a gap between the restriction plate and an inner wall of thecasing.
 15. The blasting apparatus according to claim 4, comprising arestriction plate fixed to a distal end of the screw in such a way as toform a gap between the restriction plate and an inner wall of thecasing.
 16. The blasting apparatus according to claim 3, wherein thestorage container, the volumetric feeder, and the nozzle configure aunit, the blasting apparatus comprising a movement mechanism relativelymoving the unit with respect to an object to be processed.
 17. Avolumetric feeder supplying an abrasive to a nozzle configured to blast,the volumetric feeder comprising: a casing extending in a horizontaldirection, defining a space on an inside, and including an introductionport configured to introduce the abrasive to the space, and a supplyport opened toward a lower side in a position separated from theintroduction port in a horizontal direction; and a screw including arotational shaft housed in the casing, the rotational shaft extending inthe horizontal direction, the screw configured to carry the abrasive inthe space toward the supply port from the introduction port by rotatingabout the rotational shaft; wherein the screw is housed in the casing insuch a way as not to overlap the supply port in a vertical direction.